Grid structure for electron discharge tubes



y 7, 7. L. K. PARKER 2,421,161

GRID STRUCTURE FOR ELECTRON DISCHARGE I UBES Filed June 4, 1945 INVENTOR LESLlE KEARTQN PARKER ATTORNEY Patented May 27, 1947 GRID STRUCTURE FOR ELECTRON DISCHARGE TUBES Leslie Kearton Parker, Liverpool, England, as-

signor to Automatic Electric Laboratories Inc, Chicago, 111., a corporation of Delaware Application June 4, 1945, Serial No. 597,462 In Great Britain July 7, 1944 3 Claims. 1

The present invention relates to thermionic valves and is more particularly concerned with valves of the type including at least one grid to which varying potentials can be applied for the purpose of influencing the flow of electrons between the other electrodes.

In simple valves of the triode type as generally employed the grid is formed of a number of Wires of circular cross-section located in a plane parallel or substantially parallel to the cathode and/or anode. Since the electrostatic field round each separate grid wire is circular or substantially so, the efiect for the grid as a whole is that the anode current does not change linearly with change of grid potential. Such a linear change is highly desirable since it would simplify many of the problems encountered in thermionic valve technique.

According to the invention improved linearity in the control action of the grid of a thermionic valve is obtained by the use of grid wires of noncircular cross-section preferably in the form of a fiat ellipse having its major axis normal to the cathode. With such a section the distribution of the electrostatic field due to the potential of the grid is such as to give a much nearer approach to for instance linear amplification,

The invention will be better understood from reference to the accompanying drawing comprising Figs. 1 and 2, of which Fig. 1 represents the arrangement normally employed, while Fig. 2 shows the modifications in accordance with the present invention. The figures show diagrammatically and on a greatly enlarged scale a partial vertical section of a thermionic valve of the beam tetrode type, only portions of the cathode and grid being shown. The cathode is represented by and it is assumed to be located more or less centrally within an evacuated glass envelope of the usual type. The grid is arranged to encircle it in the form of a wire helix and it will be seen from Fig. 1 that the wire is of ordinary circular section. The dotted circles enclosing the grid wires II are intended to represent the distribution of the electrostatic field and it may be considered that as the potential on the grid is increased the circles tend to expand. It will be seen that the gaps between equipotential surfaces produced by adjacent turns of the grid will vary in size according to a somewhat complicated law as the potential on the grid is changed and these gaps may be thought of as gates permitting the passage of electrons.

With the arrangement of Fig. 2, however, using grid wires having the section of a flat ellipse with its major axis normal to the cathode the gaps tend to be parallel-sided and the change in their size therefore tends to follow a linear law as the grid potential is changed. It will therefore be appreciated that with the use of grid wire of special section according to the invention there is an appreciable improvement in the characteristics of the valve which tend to increase its usefulness and simplify circuit design.

I claim:

1. In an electron discharge device having an anode and a cathode, an intermediate electron control electrode of a drawn flattened wire of conducting material, said wire having a cross section forming a full ellipse with its major axis in line with the electron emitting cathode.

2. In an electron discharge device having an anode and a cathode, an intermediate electron control electrode consisting of drawn flattened wire sections of conducting material coaxial to the electron emitting cathode, said wire sections having a cross section forming a full ellipse with its major axis in line with said cathode, to thereby improve the linear response ensuing due to the application of potentials to said control electrode.

3. In an electron discharge device having an anode and a cathode, an intermediate electron control electrode consisting of a drawn flattened wire of conducting material wound in a helix and coaxial to the electron emitting cathode, said wire having a cross section forming a full ellipse with its major axis in line with said cathode.

LESLIE KEARTON PARKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,000,990 Samuel May 14, 1935 2,225,077 Mouromtseff Dec. 17. 1940 2,249,016 Lubszynski et al. July 15, 1941 1,699,872 Bressler Jan. 22, 1929 

